It is well-known that alkyl ketene dimers are bonded with hydroxyl groups of cellulose molecules generally to impart thereto a water repellency. Because of such properties, alkyl ketene dimers are commonly used as cellulose treating agents to impart a water repellency to paper and other cellulosic products and, especially, as reactive sizing agents for papermaking. Typical examples of alkyl ketene dimers used for such applications include decyl ketene dimer, dodecyl ketene dimer, tetradecyl ketene dimer, hexadecyl ketene dimer, octadecyl ketene dimer and the like.
Since alkyl ketene dimers are water-insoluble, they are dispersed in water by various methods for permitting them to be used as cellulose treating agents. In this connection, it is most desirable to use such an alkyl ketene dimer as a cationic dispersion for obtaining a higher effect. This is because if the alkyl ketene dimer is dispersed in water as cationic fine particles, the bonding between the alkyl ketene dimer and cellulose which shows anionic properties in water will be promoted by the attraction between the positive charges of the fine particles of the alkyl ketene dimer and the negative charges of the cellulose. Heretofore, as cationic dispersing agents for alkyl ketene dimers used for the aforementioned purpose, several substances have been proposed including cationic starch (U.S. Pat. No. 3,130,118), polyamidepolyamine-epihalohydrin resins, cationic melamine-formaldehyde resins (U.S. Pat. No. 3,046,186) and cationic urea-formaldehyde resins. However, since dispersions obtained by using these cationic dispersing agents according to the prior art are rather poor in their stability, they cannot fully exhibit an effect as cellulose treating agents.
Accordingly, an object of the present invention is to provide a solution to the foregoing problems or drawbacks of the prior art in applying alkyl ketene dimers as cellulose treating agents.